Aquatic Ecosystem Resilience

Climate change is one of the most critical long-term threats to fish population and habitat population resilience. Increasing stream temperature, altered steam flows, and changing patterns of disturbance affect the ability of aquatic habitats to support fish populations. Forest Service scientists have built on years of research and a wealth of long-term data to: model the landscape variables influencing aquatic habitat change at multiple scales; assess the interacting effects of disturbances such as invasive species, fire, and climate; and assess population responses to these habitat changes. This research improves management efficiency, identification of the highest priority habitats for protection, approaches and management tools for restoring resilient habitats and populations, as well as strategies for protecting unique species and ecosystems.

Maximizing Efficiency of Stream Temperature Monitoring

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Photo of US Forest Service stream temperature monitoring networks - click to enlarge

Stream Temperature Monitoring Network

The Forest Service has one of the largest and most valuable stream temperature monitoring networks built from years of landscape-scale stream temperature monitoring across the Agency's extensive landbase. These lands cover the Nation's best cold water fisheries habitat in high-elevation areas where climate change effects are seen early and most intensely. In addition, Forest Service climate research is strengthened by the network of Forest Service Experimental Forests and Ranges, many of which have more than 50 years of climate data.

NorWest, Database for Stream Temperature Monitoring Data

The Forest Service leverages these data with partners to save thousands of dollars in monitoring costs. For example, a recently launched, multi-partner web-accessible database "NorthWest" made accessible stream temperature monitoring data worth an estimated $10,000,000. The data had been collected by more than 60 state, federal, tribal, and private resource agencies in previous decades. This tool supports stream temperature-climate scenarios for all fish-bearing streams across Washington, Oregon, Idaho, Montana, and Wyoming, including 52 national forests. Ultimately, this resource will facilitate better climate vulnerability assessments for aquatic species, enable coordinated management responses, and improve the efficiency of monitoring efforts by reducing redundancies.

Predicting Changes in Fish Habitats

Scientists develop new research and technology allowing managers to model the effects of climate change and other disturbance on aquatic habitats at management relevant scales.

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Tools for Stream Temperature Modeling

Forest Service scientists utilized low cost stream temperature sensors and developed new spatial statistical modeling approaches to develop regional stream temperature models and climate scenarios for 350,000 stream kilometers across the Northwest US. These models provide accurate basin- to landscape-scale stream temperature predictions under future climate scenario and are used to assess vulnerability and prioritize habitat restoration efforts for important fish species such as bull trout.

Improving Stream Temperature Models and Regional Monitoring Networks

Similar approaches have been used in the eastern US to identify watersheds most likely to support brook trout in a warmer future. Results of these studies show substantial variation in sensitivity of individual small watersheds to increases in air temperature. While groundwater resources play a large role in these differences, existing models do not adequately explain why some watersheds are less sensitive to increased air temperatures than others. Given this uncertainty, those watersheds most likely to provide brook trout refugia may be best identified by expanding existing low cost stream temperature monitoring networks. Forest Service scientists and partners are working to improve predictive power of stream temperature models and to expand regional stream temperature monitoring networks.

Forest Service scientists partnered with Earth Systems Institute to develop NetMap, a platform for rapidly conducting cost-effective watershed analysis. This tool supports climate- smart management by identifying areas of watersheds that are most likely to warm, are susceptible to erosion and mass wasting from wildfires and floods, and are currently most productive for fish. NetMap is available to forest managers in the Northwest and is being expanded to cover other western regions.

Understanding Fish Population Response to Climate Change

Forest Service research improves the understanding of climate driven habitat changes on fish population abundance and distribution.

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Modeling the Consequences of Threats on Trout Populations

Forest Service scientists are conducting long-term trout population studies to quantify and model the consequences of climate change (stream temperature and flow), invasive species, barrier removal, and other factors on fish population persistence under different climate and management scenarios. For example, in a western Massachusetts study, scientists identified spatial and season-specific flow and temperature characteristics influencing brook trout survival. This research may be expanded along a large latitudinal gradient ranging from Vermont to North Carolina to inform targeted restoration actions that could help many populations persist.

Predicting Changes in Trout Habitat

Forest Service scientists and collaborators with Trout Unlimited and USGS examined stream temperature, flow regime and biotic interactions to predict changes in habitat of four trout species in the western US. This study projects a mean 47% decline in total suitable habitat over the next 70 years due to increased temperatures, encroachment from non-native species, and warmer, rainier winters. This predicted decline could have large socioeconomic consequences and affect the region's 100 million dollar recreational trout fishing industry.

Population Resilience to Fire

Population resilience of native salmonids to fire was assessed in the Wenatchee River Watershed in Washington, and these models can be used in other areas of the western US to guide fire management activities. Forest Service scientists projected that populations of spring Chinook are resilient to fire in the Wenatchee River watershed because high intensity wildfire is not predicted close to the streams that they occupy, making effects of fire on habitat minimal. However, bull trout, which are very sensitive to stream temperature, are located in potentially isolated portions of the stream network and are thus less resilient to wildfire in this system.

Predicting the "Velocity" of Climate Change in Rivers and Streams

While most bioclimatic models predict significant range contractions for stream fish, very few biological assessments have evaluated the accuracy of these predictions. Forest Service scientists developed equations for calculating isotherm shift rates (ISRs) in streams that can be used to represent historic or future warming scenarios and can be calibrated to individual streams using local measurements of stream temperature and slope. Variability analysis suggests that short-term variation associated with inter-annual stream temperature changes will mask long-term isotherm shifts for several decades in most locations, so extended biological monitoring efforts are required to document anticipated distribution shifts. Resampling of historical sites could yield estimates of biological responses in the short term and should be prioritized to validate bioclimatic models and develop a better understanding of the effects of temperature increases on stream biotas. Read more
online here

Impact of Climate Change on Native Salmonids

It is likely that there will be wide variation in the response of native salmonids to the impact of climate change at the local scale. The Forest Service is studying variation in the susceptibility of streams with different hydrologic and thermal regimes on the Copper River to climate change and the capacity of the salmonid populations to respond to the impacts of climate change. Scientists are monitoring annual temperatures in 16 stream systems and determining the genetic and life-history diversity of coho salmon in each, which will provide insights into their resilience and adaptability. This will deliver insights to managers and regulators about priorities for management, conservation, and restoration programs.

Protecting Unique Species and Ecosystems

Forest Service scientists explore the effects of climate change on unique ecosystems and species such as Hawaiian Island Rivers, the Copper River Delta in Alaska, and the California Golden Trout.

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Science to Protect Unique Ecosystems

Long-term, stream monitoring across a precipitation gradient is being used to assess how changes in precipitation and replacement of native forests by invasive species alter water supply and habitat for culturally important aquatic species in Hawaii. In the Copper River Delta, Alaska, scientists are assessing how climate change affects the invertebrate community, and in turn, the fish and birds that depend on them. Specifically, they examined the relation between the timing of the emergence of aquatic invertebrates in the spring and the nesting of rusty blackbirds, an Endangered Species Act candidate, to identify current and future areas likely to be utilized for nesting.

Science Informing the Conservation of Unique Species

The California Golden Trout is imperiled due to introduced exotic trout, genetic hybridization, and degraded habitat, and face further stress from climate warming. Forest Service scientists are working to identify which stream areas in the Golden Trout Wilderness (California) are most vulnerable to warming and should be a prioritized for management responses to ensure habitats are more resilient to predicted changes in water temperature, flow, and snow pack.

Stream temperature monitoring networks in warmwater habitats of the southeastern US are sparse in comparison to those in coldwater habitats farther north, and the thermal ecology of these aquatic species is not well studied. Forest Service scientists began a pilot study in two watersheds in northern Mississippi to develop regional temperature monitoring protocols and to assess the relationship between stream temperature, habitat factors, and the distribution of rare fishes such as the Yazoo darter.

Research Updates

Workshop: Spatial Statistical Modeling on Stream Networks.A 1 day short overview course on spatial statistical modeling on stream networks is being offered April 15, 2013 in Boise, Idaho.
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